Heavy doping effects in the diffusion of group IV and V impurities in silicon

Studies of the diffusion of Ge, Sn, As, and Sb in Si at high donor concentrations provided by phosphorous doping have been performed. It is found that for donor concentrations, CD below ∼2×1020 cm−3, the diffusivity depends linearly on CD; for doping concentrations above ∼2×1020 cm−3, however, the diffusivity increases dramatically with increasing donor concentrations. This behavior has been successfully modeled within the vacancy–percolation model, and it is concluded that collective phenomena play a significant role at high donor concentrations.